Relationships among Contrasting Measurements of Microbial Dynamics in Pasture and Organic Farm Soils

Table 1

Microbial biomass carbon (MBC) and potentially mineralizable nitrogen (PMN) in organic farm (OF) and pasture (P) soils^a.

ID	Symbol^b	System	Fertility regime	Crop/amendment	Sampling date	MBC (mg C/kg)	PMN(mg N /kg)
C1	◆	OF	High Input^c	Tomatoes/peppers	June	369 ± 48^a	ND
NC1	◊	OF	Low Input^d	Tomatoes/pepper	June	207 ± 36^b	ND
C2	◆	OF	High Input	Tomatoes/peppers	Aug	199 ± 13^b	24 ± 6^a
CL2	▴	OF	High Input	Legumes	Aug	282 ± 29^ab	31 ± 4^a
NC2	◊	OF	Low Input	Tomatoes/peppers	Aug	156 ± 13^b	18 ± 4^a
NCL2	∆	OF	Low Input	Legumes	Aug	195 ± 12^b	19 ± 2^a
H1	▪	P	High fertility^e	None	May	1659 ± 133^c	110 ± 18^abc
L1	□	P	Low fertility^f	None	May	1931 ± 79^bc	121 ± 11^ab
H2	▪	P	High fertility	None	Sept	1915 ± 126^bc	59 ± 8^c
HM2	•	P	High fertility	Manure	Sept	2666 ± 126^a	125 ± 10^ab
L2	□	P	Low fertility^c	None	Sept	2214 ± 79^abc	85 ± 11^bc
LM2	°	P	Low fertility	Manure	Sept	2443 ± 196^ab	142 ± 13^a
Average organic farm						235 ± 77	23 ± 6
Average pasture						2138 ± 374	107 ± 30

^aMean values 𝑛=4 (± SEM) followed by the same letter are not significantly different (𝑃<0.05) as determined by Tukey’s studentized range (HSD) test.
^bSymbols used in figures throughout paper.
^cHigh input = 10–20 tons dry weight/acre of composted dairy manure + green manure (rye + vetch) applied and tilled into soil 7–10 days prior to planting.
^dLow input = green manure (rye + vetch) tilled into soil 7–10 days prior to planting.
^eHigh fertility = inorganic fertilizer, P, 134 kg/ha and K, 390 kg/ha.
^fLow fertility = inorganic fertilizer, P, 67 kg/ha and K, 195 kg/ha.